Professional occupations, including but not limited to the following: physician, surgeon, dentist, minister, architect, engineer, attorney, accountant, realtor or builder, provided further that the use shall be conducted within the principal building, that not more than one person not a resident of such building or dwelling is employed in such office and that the total area devoted to such use shall not exceed 20% of the ground floor area. In addition, sufficient off-street parking shall be provided to meet the present and anticipated needs of the use, subject to the further provisions of this chapter.